A genome-wide association study of fatness was performed using a high-density genotyping platform and two F2 resource populations established by crossing one broiler sire with dams from two unrelated highly inbred lines (Fayoumi and Leghorn). In total, 24 and 30 markers showed a significant association (P<0.01) with abdominal fat percentage in Broiler × Fayoumi (B × F) and Broiler × Leghorn (B × L) crosses, respectively. Compared to a previous scan in the same populations, with about one-tenth the marker density, the current study identified 12 additional genomic regions for fatness. These results demonstrate the power of high marker-density association studies in discovering quantitative trait loci (QTL).